Prostaglandins, thromboxanes and their metabolites have been separated using the new horizontal flow-through coil planet centrifuge (Ito, unpublished) to perform countercurrent chromatography. This continuous flow system provides separations of compounds in a manner similar to column and thin layer chromatography without the use of solid supports. Separations are produced in Teflon tubing wound helically around a supporting rod. A two phase solvent system is used with one of the two phases stationary while the other phase flows continuously due to a low pressure metering pump. Microgram quantities of material have been separated. The elution sequence of 6-keto-PGF alpha, thromboxane B2, PGF2 alpha, PGE2, 13,14-dihydro-15-keto-PGF2 alpha PGB2 and PGA2 occurs when the aqueous phase of chloroform: acetic acid: water (2:2:1) is the mobile phase.